Performance and Emission Comparison of a DI Diesel Engine Fueled by Diesel and Diesel-biodiesel Blend without and with EGR Condition

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1 27-29 September 21, Amman Jordan Performance and Emission Comparison of a DI Diesel Engine Fueled by Diesel and Diesel-biodiesel Blend without and with EGR Condition ABSTRACT Murari Mohon Roy and Md. Shazib Uddin Department of Mechanical Engineering Rajshahi University of Engineering & Technology Rajshahi-624, Bangladesh Phone and Fax: shazib397@gmail.com This study investigated the performance and emissions of a direct injection (DI) diesel engine fueled by neat diesel and 2%-8% blend of biodiesel and diesel (B2) under various load conditions and engine speeds without and with low percentage of exhaust gas recirculation (EGR) conditions. Here 1% EGR was attempted. Two parameters were measured during the engine operation: one is engine performance (brake thermal efficiency and brake specific fuel consumption), and the other is the exhaust emissions (NOx and CO). The result showed that, the brake thermal efficiency (η th ) of B2 was almost similar or a slight lower, but brake specific fuel consumption (bsfc) was a little higher than neat diesel. At no load or low load conditions without EGR, carbon monoxide (CO) was higher and oxides of nitrogen (NOx) were lower with B2 than that of diesel. However, under high load conditions, NOx became higher and CO reduced significantly with B2. In case of EGR, diesel and B2 produced no change in thermal efficiency and bsfc in comparison to non-egr. Furthermore, B2 showed higher reduction in NOx than diesel. Hence, B2 with 1% EGR can safely be used in diesel engine without any significant penalty in engine performance and with higher NOx reductions. Keywords: DI diesel engine, performance and emissions, renewable alternative fuel, biodiesel, B2, EGR. 1. INTRODUCTION The growing concern on environmental pollution caused by the extensive use of conventional fossil fuels has led to search for more environment friendly and renewable fuels. Biofuels such as alcohols and biodiesel have been proposed as alternatives for internal combustion engines [1, 2]. In particular, biodiesel has received wide attention as a replacement for diesel fuel because it is biodegradable, nontoxic and can significantly reduce toxic emissions and overall life cycle emission of carbon dioxide (CO 2 ) from the engine when burned as a fuel [3, 4]. Several countries including India have already begun substituting the conventional diesel by a certain amount of biodiesel [5]. The use of biodiesel is being promoted by EU countries to partly replace petroleum diesel fuel consumption in order to reduce greenhouse effect and dependency on foreign oil. Meeting the targets established by the European Parliament for 21 and 22 would lead to a biofuel market share of 5.75% and 1%, respectively [6]. In near future, biodiesel fuels offer a potentially very interesting alternative regarding harmful emissions. Additionally, biodiesel does not contain any sulfur. Although biodiesel has many advantages, it still has several properties, needed to be improved, such as lower calorific value, lower effective engine power, higher emission of NOx, and greater sensitivity to low temperatures. Many investigations have shown that using biodiesel in diesel engines can reduce hydrocarbon (HC), CO and particulate matter (PM) emissions but NOx emission may increase [4, 7, 8]. The increase in NOx emission serves as biodiesel s major impediment to widespread use [9]. In order to reduce this adverse effect, investigations have been carried out on different approaches for reducing NOx emission when biodiesel is used. The increase in NOx emission can be avoided through modifying the properties of the biodiesel [9] or through adjusting engine setting [1]. Szybist et al. [9] looked into the problem by considering the use of cetane improver for modifying ignition delay and the use of biodiesel with different bulk modulus for modifying fuel injection timing; both approaches have the potential for reducing NOx emission. Leung et al. [1] concluded that controlling an individual engine operating parameter cannot acquire satisfactory results on optimizing engine emission; thus, multiparameter adjustment is required for reducing simultaneously HC, NOx and PM emissions. Fernando et al. [11] reviewed the NOx reduction methods for biodiesel fuels. They concluded that the thermal NOx

2 27-29 September 21, Amman Jordan mechanism is the major contributor to NOx emission, thus NOx can be reduced through the application of water injection, water emulsified biodiesel, ignition timing retardation or exhaust gas recirculation which can lead to reduction in flame temperature. However most of these methods will normally lead to deterioration in engine performance as well. It was reported that engine parameters have significant effect on performance and emissions of diesel engine when run with biodiesel and its blend with diesel [12 14]. Hence, a study was undertaken at RUET, Bangladesh to gather information on behavior of diesel engine when operated with biodiesel and its blend with diesel at varying engine parameters. Engine tests were carried out at different engine speeds and loads without and with EGR. A low percentage of EGR was attempted to reduce NOx emissions without deterioration in engine performance. 2. EXPERIMENTAL SETUP AND MEASUREMENT A four-stroke single cylinder naturally aspirated DI diesel engine with specifications as in Table 1 was used in this experiment. Engine type Number of cylinders Bore Stroke Swept volume Table 1: Engine specifications 4-stroke DI diesel engine One 8 11 mm 553 cc Compression ratio 16.5:1 Rated power kw@18 rpm Fuel injection timing 24 BTDC All experimental data were taken at various engine speeds after engine warm-up. The diesel fuel used in this study was available in the local market. Loads were measured by electric dynamometer. Corresponding to each data point, exhaust emissions and fuel consumption were measured for diesel and B2. A flue gas analyzer (IMR 14) was used to measure CO and NOx of exhaust gases Production of Soy Biodiesel The most common method of biodiesel production is transesterification (alcoholysis) of oil (triglycerides) with methanol in the presence of a catalyst which gives biodiesel (fatty acid methyl esters, FAME) and glycerol (by-product). The basic biodiesel reaction and flow chart of soy biodiesel production is illustrated in Fig. 1. Reacting one part vegetable oil with three parts methanol gives three parts methyl esters (biodiesel) and one part glycerol. In practical terms, the volume of biodiesel will be equal to the input volume of vegetable oil. Soy biodiesel was produced by transesterification process in this study. Methanol was used as alcohol and NaOH as lye catalyst. Instead of methanol and NaOH, ethanol or KOH can also be used for making biodiesel. Methanol and NaOH were used in this study for lower cost. NAOH catalyst is in solid form and does not readily dissolve into methanol, it is best to start agitating the methanol in a mixer and add the catalyst slowly and carefully. The procedure to make biodiesel followed in this study is from [15]. The catalyst (3.5 grams) was dissolved into the methanol (2 ml) by vigorous stirring in a small flask. Once the catalyst completely dissolves in the methanol, the methoxide is ready to be added to the oil. Heating the oil prior to the mixing can increase the reaction rate and hence shorten the reaction time. The temperature is kept just below the boiling point of the alcohol (64.5ºC in case of methanol). The heated soybean oil (at 6ºC) is transferred into the biodiesel reactor (a blender in this study), and then, the catalyst/alcohol mixture is added into the oil (1 liter). The final mixture is stirred vigorously for half an hour in the blender in ambient pressure. A successful transesterification reaction produced two liquid phases: ester and crude glycerin.

3 27-29 September 21, Amman Jordan Crude glycerin, the heavier liquid, will collect at the bottom after several hours of settling. Phase separation can be observed within 1min and can be completed within 2 h of settling. Complete settling can take as long as 2h. Crude soy biodiesel was separated after 24 hours of settling. After separation from the glycerol phase, crude biodiesel is mainly contaminated with residual catalyst, water, unreacted alcohol, free glycerol, and soaps that were generated during the transesterification reaction. Generally, three main approaches are adopted for purifying biodiesel: water washing, dry washing, and membrane

4 27-29 September 21, Amman Jordan extraction. Since both glycerol and alcohol are highly soluble in water, water washing is very effective for removing both contaminants. It also can remove any residual sodium salts and soaps. Water washing (twice) was used in this study to wash the impurities in the crude biodiesel. After washing, finished soy biodiesel was obtained. The collection efficiency was more than 95%. 3. EXPERIMENTAL RESULTS AND DISCUSSION 3.1. Engine performance After the engine reached the stabilized working condition for each test, fuel consumption, load and exhaust emissions were measured, from which bsfc, torque and efficiency were computed. The variations of these parameters with respect to torque are presented. Figure 2 shows brake thermal efficiency (η th ) and bsfc with diesel and B2 without and with 1% EGR at 6 rpm for various engine loads. Fig. 1(a) is for non-egr and 1(b) for 1% EGR condition. It is seen that, brake thermal efficiency with B2 and neat diesel increased without and with EGR condition as the engine torque was increased. On the other hand, bsfc with B2 and neat diesel decreased without and with EGR condition as the engine torque was increased. Brake thermal efficiency with B2 without and with EGR condition is very similar or a little lower than neat diesel for various loading conditions. At low load condition, thermal efficiency with B2 and neat diesel is only about 6%. At medium load condition, it is increased to about 1%, and at high load condition, it is about 17%. Brake specific fuel consumption with B2 is a little higher than neat diesel, about 1-2% without and with EGR condition. It decreased from about 1.5 kg/kw-hr to less than.5 kg/kw-hr, when engine torque was increased from 2.45 to 9.8 N-m. Figure 3 illustrates the variation of brake thermal efficiency and bsfc with engine torque at 1 rpm without and with EGR condition for neat diesel and B2. Brake thermal efficiency with B2 and neat diesel increased without and with EGR condition, as the engine torque was increased, and bsfc with B2 and neat diesel decreased without and with EGR condition as the engine torque was increased. Brake thermal efficiency with B2 without and with EGR condition is very similar to that with neat diesel for various loading conditions. The trend is similar to that described in Fig. 2. At low load condition, thermal efficiency with B2 and neat diesel without and with EGR condition is about 16%. At medium load condition, it is increased to about 26%, and at high load condition, it is about 3%. This is the highest thermal efficiency obtained in this study. Brake specific fuel consumption with B2 is a little higher than neat diesel, about 1-3% without and with EGR condition. It decreased from about.54 kg/kw-hr to less than.3 kg/kw-hr, when engine torque is increased from 6 to 24 N-m.

5 27-29 September 21, Amman Jordan bsfc (kg/kw -hr) (%) bs fc (kg/kw-hr) η th (% ) (a) Non- EGR B2 bsfc (kg/kw- (% ) η th bs fc (k g /k w -hr) (% ) (1% EGR) B2 (1% EGR) Fig. 2: Brake thermal efficiency and bsfc with diesel and B2 without and with EGR condition at 6 rpm η th 1 (a) Non-EGR B η th (1% EGR) B2 (1% EGR) Fig. 3: Brake thermal efficiency and bsfc with diesel and B2 without and with EGR condition at 1 rpm Figure 4 shows brake thermal efficiency and bsfc with diesel and B2 without and with 1% EGR at 12 rpm for various engine loads. Brake thermal efficiency and bsfc with diesel and B2 are similar to that in Figs. 2 and 3. At low load condition, thermal efficiency with B2 and neat diesel is about 15%. At medium load condition, η th is increased to about 2%, and at high load condition, η th is less than 2%. Brake specific fuel consumption with B2 is always a little higher than neat diesel, about 2-4% without and with EGR condition. It decreased from about.59 kg/kw-hr to less than.4 kg/kw-hr, where engine torque is increased from 7.5 to 3 N-m.

6 27-29 September 21, Amman Jordan bsfc (kg/kw-hr) (%) η th (a) Non-EGR B bsfc (kg/kw-hr) (% ) η th (1% EGR) B2 (1% EGR) Fig. 4: Brake thermal efficiency and bsfc with diesel and B2 without and with EGR condition at 12 rpm 3.2. Engine emissions Figure 5 shows the variation of CO and NOx emissions with engine torque without and with EGR at 6 rpm for neat diesel and B2. Fig. 5(a) is for non-egr and 5(b) for 1% EGR condition. From the figure, it is seen that at no load or low load conditions CO emission with B2 is always higher than neat diesel without and with EGR condition. However, CO decreased with B2 and increased with neat diesel with increasing engine load. NOx (ppm) CO (ppm) (a) Non-EGR B2 NOx (ppm) CO (ppm) (1% EGR) B2 (1% EGR) Fig. 5: CO and NOx emissions with diesel and B2 without and with EGR condition at 6 rpm Improved combustion as well as less CO was expected with biodiesel than diesel due to biodiesel s inherent O 2 content. However, at no or low load conditions, biodiesel showed poorer combustion and higher CO than diesel. Higher viscosity and boiling temperature of biodiesel as well as lower combustion temperature at low engine speed produced improper local mixture producing higher CO emission than diesel. The trend is reversed after a certain load. When the fuel-air equivalence ratio (φ) increases at higher engine loads, O 2 in biodiesel helps to produce less CO, whereas CO increases with diesel combustion. NOx emission without EGR with B2 and diesel is very similar. However, NOx reduction with EGR for B2 fuel is higher than diesel fuel. Specific heat of biodiesel is higher than that of neat diesel. Therefore, higher amount of combustion heat is absorbed by the recirculated biodiesel exhaust lowering the combustion temperature. This helps to reduce higher NOx than diesel.

7 27-29 September 21, Amman Jordan Figure 6 illustrates the variation of CO and NOx emission with engine torque without and with EGR condition at 1 rpm for diesel and B2. At no load condition, CO emission with B2 is higher than that of neat diesel without and with EGR condition. CO with B2 is decreased than that of neat diesel when engine load is increased. At higher engine speed of 1 rpm, only no load condition produced poorer combustion with higher CO emission with B2 than neat diesel. CO (ppm) NOx (ppm) CO (ppm) NOx (ppm) (a) Non-EGR B2 CO (ppm) NOx (ppm) CO (ppm) NOx (ppm) (1% EGR) B2 (1% EGR) Fig. 6: CO and NOx emissions with diesel and B2 without and with EGR condition at 1 rpm. Without EGR, NOx emission with B2 at lower load condition is lower and at higher load condition it is higher than that of neat diesel. However, with EGR B2 always produced lower NOx than that of neat diesel similar to that in Fig. 5. Figure 7 shows the variation of CO and NOx emission with engine torque without and with EGR condition at 12 rpm (a) Non-EGR B (1% EGR) B2 (1% EGR) Fig. 7: CO and NOx emissions with diesel and B2 without and with EGR condition at 12 rpm. At no load condition, CO with B2 is slightly higher than that of neat diesel, and with increasing load CO is always lower than diesel fuel without and with EGR condition. Here also NOx reduction with B2 is higher than neat diesel fuel. From experimental results it is understood that biodiesel combustion at low temperature condition deteriorates combustion quality and produces higher CO without or with low percentage of EGR due to higher viscosity of biodiesel and improper mixture formation. With EGR operation biodiesel reduced higher NOx than diesel due to higher specific heat of biodiesel exhaust, for which recirculated exhaust gas at EGR absorb higher amount of combustion heat.

8 27-29 September 21, Amman Jordan Figure 7 shows PM emissions at different engine speeds and loads for various fuels. At 65 rpm, PM emission at no load with diesel fuel is about 45 mg/m3 of exhaust gas. It increased to about 175 mg/m3 at full load operation, about four times than no load condition. B2 showed the PM about 2% and B1 about 3% less than diesel throughout the operation range. At 95 rpm, PM emission at no load with diesel fuel is about 93 mg/m3 of exhaust gas. It increased to about 266 mg/m3 at full load operation, about three times than no load condition. B2 showed the PM about 2% and B1 about 3% less than diesel throughout the operation range. At 12 rpm, PM emission at no load with diesel fuel is about 1 mg/m3 of exhaust gas. It increased to about 68 mg/m3 at full load operation, about seven times than no load condition. Again B2 showed the PM about 2% and B1 about 3% less than diesel throughout the operation range. Shobokshy (1984) and Sharmaet al. (25) have reported that particulate concentration increases with increased engine load; the same trend is obtained in present study. Particles are mainly 46 formed during diffusion combustion, and most of the combustion process is diffusive at high load. Therefore, high levels of PM were exhausted at full load operations at different engine speeds. The oxygen content of biodiesel helped in reducing PM. Higher reduction was expected at higher load operations, but the reduction throughout the engine load was almost constant. The other reason of reduction in PM with biodiesel and blend is attributed to near absence of aromatic compounds and sulphur in biodiesel.

9 27-29 September 21, Amman Jordan 4. CONCLUSION The following conclusions can be drawn from the experimental investigation. 1. B2 showed very similar thermal efficiency to that of the level of diesel without and with low EGR conditions. 2. The bsfc of B2 is about 1-4% higher than that of diesel without or with EGR. 3. At no load or low load conditions, B2 produced higher CO than diesel, but at high load condition B2 produced significantly lower CO than diesel without or with EGR condition. 4. At no load or low load condition without EGR, B2 produced lower NOx than the neat diesel, but at higher load condition NOx emission with B2 is higher than diesel. With 1% EGR condition, B2 always produced lower NOx than that of diesel at all engine speed and load conditions. 5. The oxygen content of biodiesel helped in reducing PM. This might be due to lower sulphur and aromatic content of biodiesel. B2 showed the PM about 2% and B1 about 3% less than diesel at all operating conditions. REFERENCES [1] Agarwal AK., 27. Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energ Combust Sci; 33: [2] Demirbas A., 27. Progress and recent trends in biofuels. Prog Energ Combust Sci; 33:1 18. [3] Cvengros J, Povazanec F.,1996. Production and treatment of rapeseed oil methyl esters as alternative fuels for diesel engines. Bioresour Technol; 55: [4] USEPA, 22. A comprehensive analysis of biodiesel impacts on exhaust emissions. EPA42-P [5] H. Raheman, S.V. Ghadge, 28. Performance of diesel engine with biodiesel at varying compression ratio and ignition timing, Fuel 87; [6] Magín Lapuerta, José M. Herreros, Lisbeth L. Lyons, Reyes García-Contreras, Yolanda Briceño, 28. Effect of the alcohol type used in the production of waste cooking oil biodiesel on diesel performance and emissions, Fuel 87; [7] Schumacher LG, Borgelt SC, Fosseen D, Goeta W, Hires WG., Heavy-duty engine exhaust emissions tests using methyl ester soybean oil/diesel fuel blends. Bioresour Technol ; 57:31 6. [8] Sharp CA, Howell SA, Jobe J., 2. The effect of biodiesel fuels on transient emissions from modern diesel engines-part I: regulated emissions and performance. SAE Tech Pap Ser; No [9] Szybist J, Simmons J, Druckenmiller M, Al-Qurashi K, Boehman A, Scaroni A., 23. Potential methods for NOx reduction from biodiesel. SAE Tech Pap; No [1] Leung DYC, Luo Y, Chan TL., 26. Optimization of exhaust emissions of a diesel engine fuelled with biodiesel. Energ Fuel; 2: [11] Fernando S, Hall C, Jha S., 26. NOx reduction from biodiesel fuels. Energ Fuel ; 2: [12] Laforgia D, Ardito V., Biodiesel fuelled IDI engines: performances, emissions and heat release investigation. Bioresour Technol; 51:53 9. [13] Monyem A, Gerpen JV, Canakci M., 21. The effect of timing and oxidation on emissions. TransASAE ; 44(1):35 42.

10 27-29 September 21, Amman Jordan [14] P a n d e y K C. 25. Investigations on use of soybean oil as a substitute fuel for diesel engines. Unpublished PhD thesis, IIT Kharagpur. [15] Make your own biodiesel,

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